Keyboard-operated devices such as pocket-sized electronic calculators and the like usually embody several flat dielectric cards having circuit paths provided on the cards. These cards are commonly made by covering one or both flat sides of the cards with a layer of copper and by etching the copper layers to form the desired circuit paths on the cards. One of the cards having such circuit paths on one side is then provided with contact means on the opposite side of the card, these contact means having portions extending through the card to electrically connect to the circuit paths on the card. Switching means such as snap-acting disc elements are also located on the opposite side of the card in selected relation to the card contacts and key means are provided for actuating the snap-acting switches to bridge selected pairs of contacts for completing selected circuits. Electronic components are then mounted on the other dielectric card with component terminals connected to selected circuit paths on the card and means are provided for interconnecting circuit paths on the two cards in a desired manner to form a complete electronic apparatus.
In this prior art approach to manufacture of keyboard-operated devices, the etched circuit cards represent a very significant element of cost. More important, the use of such cards imposes requirements for a number of assembly operations which must be performed with great care to avoid misalignments between various parts of the devices. For example, such care must be exercised in mounting contacts on the cards, in locating snap-acting elements to bridge the contacts, and in interconnecting circuit paths on the two dielectric cards. As a result, such prior art keyboard devices have been characterized by high material costs and by high assembly costs. The devices are also of somewhat limited durability and are subject to misalignments of different parts of the devices during use.
It is an object of this invention to provide a novel and improved keyboard apparatus; to provide such an apparatus which is of simple, compact and inexpensive structure; to provide novel and improved methods for making such apparatus; to provide such methods and apparatus which are characterized by economy of assembly; to provide such methods and apparatus which permit convenient apparatus assembly with a high degree of accuracy; and to provide such keyboard apparatus which is also rugged and reliable in use.
Briefly described, the novel and improved keyboard apparatus of this invention is made by forming a dielectric card with a plurality of recesses in one card side and, preferably, with a plurality of apertures extending through the card. Typically, the dielectric card is molded and each recess is formed with a recess bottom at one surface level, with a shoulder extending at least partly around the recess bottom forming a second surface level, and with a recess wall upstanding from the recess shoulder. This molded, multisurface level card is then subjected to an additive-type of metal deposition procedure to form electrically conductive contacts and circuit paths on the various surface levels of the card. Typically, first electrical contacts are deposited on each of the recess shoulders, complementary electrical contacts are formed at the bottom of each recess, and a circuit path pattern is deposited on one or both sides of the card and within selected card apertures, these circuit paths being electrically connected to the card contacts in a selected manner. Snap-acting electrically-conductive dished elements are then disposed in respective card recesses to be located by the walls of the recess in engagement with first contacts in the recesses and to be normally spaced from the complementary contacts in the recesses. Preferably, a flexible plastic film is secured over the recessed card side for dust sealing the dished elements and the contacts within each recess. Key means are then mounted on the recessed card side for selectively moving the snap-acting elements to an inverted dished configuration so that the snap-acting elements further engage the complementary contacts in the recesses to close selected circuits. Various electronic components necessary for completing the keyboard apparatus are mounted on the same dielectric card by inserting component terminals in card apertures to be electrically connected to selected circuit paths on the card. Preferably electrically conductive elastomers are secured in these card apertures for detachably holding the component terminals in the apertures while electrically connecting the component terminals to the circuit paths on the card.
In this arrangement, a single dielectric card is provided with all necessary electrical contact means and circuit path means in an inexpensive and reliable way, the contacts and circuit paths being connected to each other in the desired manner. The multilevel structure of the dielectric card properly locates the snap-acting switch elements relative to the card contacts for assuring proper operation of the snap-acting elements as device switches. These snap-acting switches are easily and reliably dust-sealed in the apparatus and electronic components required for completing the apparatus are easily mounted on the single dielectric card and are properly connected to circuit paths on the card in an economical and reliable way. Thus, the described apparatus is of very simple and economical construction, is easily and reliably assembled at low cost, and is rugged and compact during use.